Objective: The aim of this study was to clarify the association of physical frailty with behavioral and psychological symptoms of dementia (BPSD) and caregiver burden in patients with Alzheimer’s disease (AD).

Methods: The subjects were 1,193 AD patients who presented to the Memory Clinic at the National Center for Geriatrics and Gerontology of Japan during the period from October 2010 to February 2015 (mean±SD age=78.8±6.3 years; female, 68.6%). AD was diagnosed based on the criteria of the National Institute on Aging and Alzheimer’s Association workgroups. The Frailty Index (FI) was calculated as the ratio of actual to 38 potential deficits. BPSD and caregiver burden were assessed by using the Dementia Behavior Disturbance Scale (DBD) and the Japanese version of Zarit Burden Interview (J-ZBI). Multiple linear regression analyses and structural equation modeling (SEM) were performed to examine the relationship between the FI, DBD, and J-ZBI.

Results: The subjects’ mean FI score was 0.16±0.10, with 663 (55.6%) and 198 (16.6%) subjects shown to be pre-frail (0.08≤FI<0.25) and frail (FI≥0.25), respectively. Multiple linear regression analyses and SEM showed that the FI was independently associated with both DBD (β=0.30, P<.001) and J-ZBI (β=0.13, P<.001). Moreover, when the FI was considered as a categorical variable, even pre-frailty was associated with increased DBD score (β=0.16, P<.001) and J-ZBI score (β=0.09, P=.003).

Conclusions: The presence of not only physical frailty but also pre-frailty, as determined by the FI, could increase BPSD and caregiver burden in patients with AD.